1. Field of the Invention
The present invention relates to a magnetic antenna formed by winding a coil conductor around a magnetic layer. The present invention also relates to an antenna device and an electronic apparatus.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2007-19891 discloses a magnetic antenna formed by winding a coil conductor around a magnetic layer so that its winding axis direction and its layer-stacking direction are orthogonal to each other. In that magnetic antenna, an insulation layer is formed on the outmost layer of the magnetic layer to prevent the coil conductor from making contact with any external metal object. In this magnetic antenna, the insulation layer is provided with a conducting layer to prevent changes in characteristics of the magnetic antenna and shifting in resonant frequency when the magnetic antenna is brought close to a metal object.
When an antenna is used in an HF band, it is necessary to connect a low pass filter (LPF) to the antenna so as to cut harmonic components. Thus, it is also necessary to secure a mounting space on a substrate to mount the LPF. A magnetic antenna such as described in Japanese Unexamined Patent Application Publication No. 2007-19891 may reduce the mounting space of the magnetic antenna. However, it is still necessary to secure the mounting space of the LPF. Thus, in Japanese Unexamined Patent Application Publication No. 2007-19891, there is an issue that a reduction in size may be difficult to achieve for an apparatus on which the magnetic antenna is mounted.